<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<div id="app">
  <h1 v-if="isShow">{{message}}</h1>
  <h1 v-else>{{info}}</h1>
</div>

<script src="../js/vue.js"></script>
<script>
  //let(变量)和const(常量)
    const app = new Vue({
      el: '#app',
      data: {
        message: '中国牛蛙！',
        info: '华夏雄起！',
        isShow: true
      }
    })
</script>
</body>
</html>